Control and power module for brushless motor

ABSTRACT

An electronic module is provided for a power tool having an electric motor. The module includes a printed circuit board (PCB) having a first surface and a second surface; first set of power switches mounted on the first surface of the PCB; second set of power switches mounted on the PCB and electrically coupled to the first power switches forming an inverter bridge circuit for driving the electric motor; a first heat sink surface-mounted on the first surface of the PCB and having a planar main body disposed over the first power switches; a module housing arranged to receive the PCB therein; and a second heat sink secured to the module housing in thermal communication with the first heat sink to transfer heat from the first power switches.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/396,420 filed June Sep. 19, 2016, which is incorporated herein byreference in its entirety.

FIELD

This disclosure relates to brushless motor controls. More particularly,the present invention relates to a module including control and powercircuitry for driving a brushless motor.

BACKGROUND

Brushless DC (BLDC) motors have been used in recent years in variouscordless power tools. While BLDC motors provide many advantages overuniversal and permanent magnet DC motors, challenges exist inincorporating BLDC motors into many power tools depending on powerrequirements and specific applications of tool.

To drive a BLDC motor, a series of power switching components aretypically provided to control the flow of current to the motor windings.These power switching components generate significant amount of heat.Thermal control of such components generally presents many challenges,particularly in compact power tool applications. This is particularlytrue for tools used in environments where dust and particulate from theworkpiece is abundant, making it difficult to create a clean air flowwithin the tool to cool both the motor and the power switchingcomponents.

The power switching components are controlled via a micro-controller orother control hardware. The micro-controller also receives positionalsignals related to the rotational position of the motor from a series ofsensors (e.g., Hall sensors). The wiring connectivity between themicro-controller, the power switching components, and the positionalsensors is often burdensome and susceptible to failure. Again suchfailures are more abundant in power tools used in harsh environmentswhere dust and vibration can interfere with or break the electricalconnections.

SUMMARY

According to an embodiment of the invention, an electronic module isprovided for a power tool having an electric motor. In an embodiment,the electronic module includes a printed circuit board (PCB) having afirst surface and a second surface; first (high-side) power switchesmounted on the first surface of the PCB; second (low-side) powerswitches mounted on the PCB and electrically coupled to the first powerswitches forming an inverter bridge circuit for driving the electricmotor; a first heat sink surface-mounted on the first surface of the PCBand having a planar main body disposed over the first power switches; amodule housing arranged to receive the PCB therein; and a second heatsink secured to the module housing in thermal communication with thefirst heat sink to transfer heat from the first power switches.

In an embodiment, each of the second power switches is mounted on thesecond surface the PCB substantially opposite a respective first powerswitch.

In an embodiment, a first set of conductive tracks is disposed on thefirst surface of the PCB and electrically coupled to drains of the firstpower switches, and a second set of conductive tracks is disposed on thesecond surface of the PCB and electrically coupled to sources of thesecond power switches.

In an embodiment, the PCB includes through-holes between the first andsecond sets of conductive tracks, and power terminals each having legsreceived within the through-holes to electrically connect thecorresponding conductive tracks.

In an embodiment, each power terminal includes a radial peripheral slotarranged to receive and make electrical contact with a correspondingmotor terminal.

In an embodiment, peripheral slots are disposed around the PCB forpass-through of the motor terminals.

In an embodiment, positional sensors are disposed angularly around acenter of the first surface of the PCB.

In an embodiment, the module housing includes a planar portion, and aplurality of openings disposed in the planar portion angularly around acenter of the module housing and corresponding to the positionalsensors.

In an embodiment, the module housing includes a casing molded around thesecond heat sink.

In an embodiment, the second heat sink includes a ring-shaped or aC-shaped profile.

In an embodiment, the second heat sink has a surface area that is two tofour times larger than a surface area of the first heat sink.

In an embodiment, a first surface of the second heat sink is positionedin contact with or in close proximity to the planar main body of thefirst heat sink, and a second surface of the second heat sink is atleast partially exposed on an outer portion of the module housing facingthe electric motor.

In an embodiment, the module housing and the PCB each includes athrough-hole arranged to receive a shaft of the electric motor.

In an embodiment, the first power switches are disposed on one side ofthe first surface of the PCB.

According to an embodiment of the invention, an electronic module isprovided for a power tool having an electric motor. In an embodiment,the electronic module includes a printed circuit board (PCB) beingsubstantially disc-shaped and including a first surface and a secondsurface, where the first surface has a power portion and a controlportion and a second surface. In an embodiment, the electronic modulefurther includes first (high-side) power switches mounted on the firstsurface of the PCB within the power portion; second (low-side) powerswitches mounted on the PCB and electrically coupled to the first powerswitches forming an inverter bridge circuit for driving the electricmotor; a heat sink having legs mounted on the first surface of the PCBand having a planar main body extending from the legs substantially inparallel to the of the PCB over the first power switches; a controllermounted on the PCB and configured to control a switching operation ofthe first power switches and the second power switches; and positionalsensors mounted on the first surface of the PCB substantiallyequidistantly from a center of the PCB within the control portion incommunication with the controller to provide positional signals relatedto a rotational position of the electric motor to the controller.

In an embodiment, the controller is mounted on the first surface of thePCB within the control portion.

In an embodiment, the first power switches are disposed equidistantlyfrom the center of the PCB. In an embodiment, the first power switchesare disposed at an angular distance of approximately 60 degrees apart.

In an embodiment, power terminals are disposed around a periphery of thePCB and angularly corresponding to the power switches. In an embodiment,the power terminals are disposed to receive motor terminals therein toelectrically connect the first power switches to the electric motor.

In an embodiment, a module housing is arranged to receive the PCBtherein. In an embodiment, the module housing includes a planar portionin parallel to the PCB and openings disposed in the planar portionangularly around a center of the module housing to receive thepositional sensors therein.

In an embodiment, a gasket is disposed between the planar portion of themodule housing and the first surface of the PCB to seal the outerperimeters of the openings.

In an embodiment, the module housing includes a heat sink in thermalcommunication with the first power switches. In an embodiment, the heatsink is exposed on an outer surface of the module housing facing themotor.

In an embodiment, the heat sink includes a ring-shaped or a C-shapedprofile.

In an embodiment, a potting compound is provided to substantially coverboth surfaces of the PCB within the module housing.

According to an embodiment of the invention, an electronic module isprovided for a power tool having an electric motor. In an embodiment,the electronic module includes a printed circuit board (PCB) beingsubstantially disc-shaped; power switches mounted on the PCB forming aninverter bridge circuit for driving the electric motor; a controllermounted on the PCB and configured to control a switching operation ofthe power switches; positional sensors mounted on the PCB substantiallyequidistantly from a center of the PCB within the control portion and incommunication with the controller to provide positional signals relatedto a rotational position of the electric motor to the controller; and amodule housing arranged to receive the PCB therein. In an embodiment,the module housing includes a planar portion in parallel to the PCB andopenings disposed in the planar portion angularly around a center of themodule housing to receive the positional sensors therein.

In an embodiment, a first heat sink is mounted on the PCB in thermalcommunication with at least one of the power switches.

In an embodiment, a second heat sink is secured to the module housing inthermal communication with the first heat sink to transfer heat from thepower switches.

According to an embodiment of the invention, a power tool is providedincluding a housing arranged to house the electric motor. An electronicmodule having the features described above is disposed within thehousing adjacent the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of this disclosure in any way.

FIG. 1 depicts a perspective view of an exemplary power tool, accordingto an embodiment of the invention;

FIGS. 2 and 3 depict perspective exploded views of the exemplary powertool, according to an embodiment of the invention;

FIG. 4 depicts a perspective exploded view of a brushless DC (BLDC)motor disposed within the power tool, according to an embodiment of theinvention;

FIG. 5 depicts an exemplary circuit block diagram for a battery-poweredpower tool including a motor control circuit, according to anembodiment;

FIG. 6 depicts an exemplary circuit diagram of an three-phase invertercircuit for driving a BLDC motor, according to an embodiment;

FIGS. 7A and 7B depict partially-exploded and perspective views of theBLDC motor and a combined control and power module provided adjacent theend of the motor, according to an embodiment;

FIGS. 8A and 8B depict front and back perspective views of a printedcircuit board (PCB) for use in the control and power module, accordingto an embodiment;

FIG. 9 depicts a perspective view of the PCB with a primary heat sinkmounted on its first surface, according to an embodiment;

FIGS. 10A and 10B depict perspective views of the PCB with powerterminals secured on its second surface, according to an embodiment;

FIG. 11 depicts a perspective view of the PCB with anelectrically-isolating thermally-conductive gap pad disposed on theprimary heat sink, according to an embodiment;

FIGS. 12A-12C depict various views of the module housing of the combinedcontrol and power module, according to an embodiment;

FIGS. 13A and 13B depict top views of the module housing provided with agasket for sealing the outer perimeter of the module housing openings,according to an embodiment;

FIG. 14 depicts an exploded view of the combined control and powermodule, according to an embodiment;

FIGS. 15A and 15B depict top and bottom assembled views of the combinedcontrol and power module, according to an embodiment;

FIG. 16 depicts a top perspective view of the combined control and powermodule with a potting combined applied, according to an embodiment; and

FIG. 17 depicts a bottom perspective view of the combined control andpower module with an adhesive applied to the housing openings, accordingto an embodiment.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

The following description illustrates the claimed invention by way ofexample and not by way of limitation. The description clearly enablesone skilled in the art to make and use the disclosure, describes severalembodiments, adaptations, variations, alternatives, and uses of thedisclosure, including what is presently believed to be the best mode ofcarrying out the claimed invention. Additionally, it is to be understoodthat the disclosure is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. The disclosure iscapable of other embodiments and of being practiced or being carried outin various ways. Also, it is to be understood that the phraseology andterminology used herein is for the purpose of description and should notbe regarded as limiting.

As shown in FIGS. 1-3, according to an embodiment of the invention, apower tool 10 is provided including a housing 12 having a gear case 14,a motor case 16, a handle portion 18, and a battery receiver 20. FIG. 1provides a perspective view of the tool 10. FIGS. 2 and 3 depict twoexploded views of tool 10. Power tool 10 as shown herein is an anglegrinder with the gear case 14 housing a gear set (not shown) that drivesa spindle 24 arranged to be coupled to a grinding or cutting disc (notshown) via a flange (or threaded nut) 25 and guarded by a disc guard 26.It should be understood, however, that the teachings of this disclosuremay apply to any other power tool including, but not limited to, a saw,drill, sander, and the like.

In an embodiment, the motor case 16 attaches to a rear end of the gearcase 14 and houses a motor 28 operatively connected to the gear set 22.The handle portion 18 attaches to a rear end 30 of the motor case 16 andincludes a trigger assembly 32. The battery receiver 20 extends from arear end 31 of the handle portion 18 for detachable engagement with abattery pack (not shown) to provide power to the motor 28. In anexemplary embodiment, the battery pack may be a 60 volt max lithium-iontype battery pack, although battery packs with other batterychemistries, shapes, voltage levels, etc. may be used in otherembodiments.

In various embodiments, the battery receiver 20 and battery pack may bea sliding pack disclosed in U.S. Pat. No. 8,573,324, hereby incorporatedby reference. However, any suitable battery receiver and battery backconfiguration, such as a tower pack or a convertible 20V/60V batterypack as disclosed in U.S. patent application Ser. No. 14/715,258 filedMay 18, 2015, also incorporated by reference, can be used. The presentembodiment is disclosed as a cordless, battery-powered tool. However, inalternate embodiments power tool can be corded, AC-powered tools. Forinstance, in place of the battery receiver and battery pack, the powertool 10 include an AC power cord coupled to a transformer block tocondition and transform the AC power for use by the components of thepower tools. Power tool 10 may for example include a rectifier circuitadapted to generate a positive current waveform from the AC power line.An example of such a tool and circuit may be found in US PatentPublication No. 2015/0111480, filed Oct. 18, 2013, which is incorporatedherein by reference in its entirety.

In an embodiment, the trigger assembly 32 is a switch electricallyconnected to the control module 11 as discussed above. The triggerassembly 32 in this embodiment is an ON/OFF trigger switch pivotallyattached to the handle 18. The trigger 32 is biased away from the handle18 to an OFF position. The operator presses the trigger 32 towards thehandle to an ON position to initiate operation of the power tool 10. Invarious alternate embodiments, the trigger assembly 32 can be a variablespeed trigger switch allowing the operator to control the speed of themotor 28 at no-load, similar to variable-speed switch assembly disclosedin U.S. Pat. No. 8,573,324, hereby incorporated by reference. However,any suitable input means can be used including, but not limited to atouch sensor, a capacitive sensor, or a speed dial.

In an embodiment, power tool 10 described herein is high-power powertool configured to receive a 60V max battery pack or a 60V/20Vconvertible battery pack configured in its 60V high-voltage-rated state.The motor 28 is accordingly configured for a high-power application witha stator stack length of approximately 30 mm. Additionally, as laterdescribed in detail, the power module 34, including its associated heatsink, is located within the motor case 16 in the vicinity of the motor28. Additionally and/or alternatively, power tool 10 may be have alow-voltage rating (e.g., 20V) or mid-voltage rating (e.g., 40V) adaptedto receive a 20V max or a 40V max battery pack.

While embodiments depicted herein relate to a DC-powered power toolpowered by a battery pack, it is noted that the teachings of thisdisclosure also apply to an AC-powered tool, as disclosed in US PatentPublication No. 2015/0111480, which is incorporated herein by referencein its entirety. In this embodiment, a power cord may be providedinstead of battery receiver 20. The power tool 10 may be configured toreceive AC supply having a nominal voltage of, for example, 120 VAC.Alternatively, power tool 10 may be configured to receive AC supplyhaving a nominal voltage of, for example, 230 VAC.

Additionally and/or alternatively, the teachings of this disclosure alsoapply to an AC/DC power tool, as disclosed in WO2015/179318 filed May18, 2015, which is incorporated herein by reference in its entirety. Inthis case, the power tool may be provided with a battery receptacle 20as well as a power cord (not shown). Alternatively, an AC/DC poweradaptor may be provided to supply one of AC or DC power to the powertool via the battery receiver 20, as described in detail in the '318application.

FIG. 4 depicts an exploded view of the motor 28, according to anembodiment. As shown herein, the motor 28 is a three-phase brushless DC(BLDC) motor having a can or motor housing 29 sized to receive a statorassembly 70 and a rotor assembly 72. Various aspects and features of themotor 28 are described herein in detail. It is noted that while motor 28is illustratively shown as a part of an angle grinder, motor 28 may bealternatively used in any power tool or any other device or apparatus.

In an embodiment, rotor assembly 72 includes a rotor shaft 74, a rotorlamination stack 76 mounted on and rotatably attached to the rotor shaft74, a rear bearing 78 arranged to axially secure the rotor shaft 74 tothe motor housing 29, a sense magnet ring 90 attached to a distal end ofthe rotor shaft 74, and fan 37 also mounted on and rotatably attached tothe rotor shaft 74. In various implementations, the rotor laminationstack 76 can include a series of flat laminations attached together via,for example, an interlock mechanical, an adhesive, an overmold, etc.,that house or hold two or more permanent magnets (PMs) therein. Thepermanent magnets may be surface mounted on the outer surface of thelamination stack 76 or housed therein. The permanent magnets may be, forexample, a set of four PMs that magnetically engage with the statorassembly 70 during operation. Adjacent PMs have opposite polarities suchthat the four PMs have, for example, an N-S-N-S polar arrangement. Therotor shaft 74 is securely fixed inside the rotor lamination stack 76.Rear bearing 78 provide longitudinal support for the rotor 74 in abearing pocket (described later) of the motor housing 29.

In an embodiment, stator assembly 70 includes a generally cylindricallamination stack 80 having center bore configured to receive the rotorassembly 72. Lamination stack 80 further includes a plurality of statorteeth extending inwardly from a stator ring towards the center bore. Thestator teeth define a plurality of slots there between configured. Aplurality of coil windings 86 are wound around the stator teeth 82 intothe slots. Coil windings 86 may be wound and connected together invarious configurations, e.g., in a wye or a delta configuration. In anembodiment, where motor 28 is a three-phase BLDC motor, three coilwindings 86 may be wound on six stator teeth 82, with each coil winding86 being wound on two opposing teeth 82 (e.g., U and U′, V and V′, and Wand W′). Terminals 104 are coupled to the coil windings 86. In anembodiment, the location of two opposing coils (e.g., W and W′) may beswitched and the stator routed accordingly in order to provide the threeterminals 110 at 60 degrees apart.

In an embodiment, fan 37 of the rotor assembly 72 includes a back plate60 having a first side 62 facing the motor case 16 and a second side 64facing the gear case 14. A plurality of blades 66 extend axiallyoutwardly from first side 62 of the back plate 60. Blades 64 rotate withthe rotor shaft 44 to generate an air flow as previously discussed. Whenmotor 28 is fully assembled, fan 37 is located at or outside an open endof the motor housing 28 with a baffle 330 arranged between the statorassembly 70 and the fan 37. The baffle 33 guides the flow of air fromthe blades 64 towards the exhaust vents 58.

The operation of a BLDC motor is typically controlled via a power moduleincluding a series of semiconductor switches (e.g., FETs or IGBTs)configured as a three-phase inverter circuit and provided between thepower supply and the motor, and a control module including amicrocontroller that manages motor commutation by controlling theswitching operation of the power module switches. The control module maybe coupled to the trigger switch (or other variable-speed input unit) toregulate the amount of current being supplied to the motor from thepower source by controlling a pulse-width-modulate (PWM) duty cycle ofthe power module switches. The control module is also coupled to aseries of positional sensors (e.g., Hall sensors) provided in closeproximity to the motor sense magnet ring 90.

Referring to FIG. 5, a circuit block diagram of power tool 10 includinga motor 28 and a motor control circuit 204 is depicted, according to anembodiment. In an embodiment, motor control circuit 204 includes a powerunit 206 and a control unit 208. In FIG. 5, power tool 10 received DCpower from a DC power source such as a battery pack via B+ and B−terminals.

In an embodiment, power unit 206 may include a power switch circuit 226coupled between the power source B+/B− terminals and motor windings todrive BLDC motor 28. In an embodiment, power switch circuit 226 may be athree-phase bridge driver circuit including six controllablesemiconductor power devices (e.g. FETs, BJTs, IGBTs, etc.).

In an embodiment, control unit 208 may include a controller 230, a gatedriver 232, a power supply regulator 234, and a power switch 236. In anembodiment, controller 230 is a programmable device arranged to controla switching operation of the power devices in power switching circuit226. In an embodiment, controller 230 receives rotor rotational positionsignals from a set of position sensors 238 provided in close proximityto the motor 28 rotor. In an embodiment, position sensors 238 may beHall sensors. It should be noted, however, that other types ofpositional sensors may be alternatively utilized. Controller 230 mayalso receive a variable-speed signal from variable-speed actuator or aspeed-dial. Based on the rotor rotational position signals from theposition sensors 238 and the variable-speed signal, controller 230outputs drive signals UH, VH, WH, UL, VL, and WL through the gate driver232, which provides a voltage level needed to drive the gates of thesemiconductor switches within the power switch circuit 226 in order tocontrol a PWM switching operation of the power switch circuit 226.

In an embodiment, power supply regulator 234 may include one or morevoltage regulators to step down the power supply to a voltage levelcompatible for operating the controller 230 and/or the gate driver 232.In an embodiment, power supply regulator 234 may include a buckconverter and/or a linear regulator to reduce the power voltage of powersupply interface 128-5 down to, for example, 15V for powering the gatedriver 232, and down to, for example, 3.2V for powering the controller230.

In an embodiment, power switch 236 may be provided between the powersupply regulator 234 and the gate driver 232. Power switch 236 may be anON/OFF switch coupled to the ON/OFF trigger or the variable-speedactuator to allow the user to begin operating the motor 28, as discussedabove. Power switch 236 in this embodiment disables supply of power tothe motor 28 by cutting power to the gate drivers 232. It is noted,however, that power switch 236 may be provided at a different location,for example, within the power unit 206 between the rectifier circuit 220and the power switch circuit 226. It is further noted that in anembodiment, power tool 128 may be provided without an ON/OFF switch 236,and the controller 230 may be configured to activate the power devicesin power switch circuit 226 when the ON/OFF trigger (or variable-speedactuator) is actuated by the user.

FIG. 6 depicts an exemplary power switch circuit 226 having athree-phase inverter bridge circuit, according to an embodiment. Asshown herein, the three-phase inverter bridge circuit includes threehigh-side FETs and three low-side FETs. The gates of the high-side FETsdriven via drive signals UH, VH, and WH, and the gates of the low-sideFETs are driven via drive signals UL, VL, and WL. In an embodiment, thedrains of the high-side FETs are coupled to the sources of the low-sideFETs to output power signals PU, PV, and PW for driving the BLDC motor28.

In conventional designs, the power unit is provided on a printed circuitboard (PCB) located in the handle portion of the tool or in a locationclose to the motor. The control unit is often provided on a separate PCBin the handle portion in close proximity to the trigger switch or thepower supply interface. The positional sensors are often provided on yetanother PCB in close proximity to the motor sense magnet ring.

Designs have been proposed in recent years combining one or more ofthese modules as a part of a single package. For example, designs havebeen proposed to combine the power unit and the positional sensors on asingle PCB. However, it has not been possible to provide a singlepackage including the power unit, the control unit, and the positionalsensors, utilizing a single PCB, for many power tool applications.Specifically, ergonomics requirements of compact handheld power toolssuch as small angle grinders, combined with the high amount of heatproduced by semiconductor switching components of the power module,presents many challenges to a single module approach. Embodiments of theinvention described herein overcome these challenges.

U.S. patent application Ser. No. 14/973,226, filed Dec. 17, 2015, whichis incorporated herein by reference in its entirety, discloses a controland power module for a power tool having a brushless DC motor, where thecontrol and power module includes a printed circuit board (PCB), a powerunit having an inverter bridge circuit with three pairs of powerswitches mounted on both sides of the PCB opposite one another, and acontrol unit including a micro-controller also disposed on the PCB. Thepresent disclosure provides an improved and/or alternative control andpower module with certain advantages described herein.

Referring to the partially-exploded view of FIG. 7A and the perspectiveview of FIG. 7B, a combined control and power module 300 is providedadjacent the end of the motor 28, according to an embodiment. In anembodiment, module 300 includes a through-hole 302 formed in a modulehousing 304 that receives an end of the motor shaft 74 therein when themodule 300 is mounted to the end of the motor 28. In an embodiment,module 300 further includes a series of motor terminals 360 that receiveand electronically coupled with motor terminals 104 therein when themodule 300 is mounted to the end of the motor 28. A series of fasteners308 are received in corresponding through-holes 306 in module 300 andcorresponding receptacles 309 at the end of the motor housing 29 tosecurely hold the module 300 to the end of the motor 28.

The detailed features of combined control and power module 300 aredescribed herein with reference to FIGS. 8A through 17, according to anembodiment.

FIGS. 8A and 8B depict front and back perspective views of a printedcircuit board (PCB) 310 for use in the control and power module 300, inan embodiment. In an embodiment, PCB 310 is generally disc-shapeincluding a through-hole 312 corresponding to through-hole 302 of module300 for longitudinally receiving the motor shaft 74, and a series ofperipheral slots 314 for longitudinally receiving motor terminals 104.FIG. 8A depicts a first surface 316 of the PCB 310 and FIG. 8B depicts asecond surface 318 of the PCB 310 opposite the first surface 316. In anembodiment, the area of the PCB 310 each surface is generally divided toa power portion 320 and a control portion 340 as indicated by dashedlines in these figures.

In an embodiment, power portion 320 includes a series of high-sideswitches 322 mounted on the second surface 318 and a series of low-sideswitches 324 mounted on the first surface 316 in mirror opposite of thehigh-side switches 322. The high-side and low-side switches 322 and 324may be, for example, n-channel field-effect transistors (FETs), whichgenerate a relatively low amount of heat. Such switches are suitable formost power tool applications with a power supply in the range of 10 to60V average voltage. It must be understood, however, that other types ofsemiconductor switches such as low-heat IGBTs may be alternativelyutilizes for higher power applications. The circuit connection for thesehigh-side and low-side switches 322 and 326 was described above withreference to FIG. 6. In an embodiment, a series of high-side bootstrapcapacitors 326 and associated circuitry is also mounted on the secondsurface 318 for driving the gates of the high-side switches 322.

In an embodiment, the high-side and low-side switches 322 and 324 aredisposed in close proximity to the slots 314, at approximately equaldistances from the through-hole 312, e.g., radially between the slots314 and the through-hole 312 around a circle. In an embodiment, therespective high-side switches 322 are disposed at an angular distance ofapproximately 60 degrees apart, and the respective low-side switches 324are similarly disposed at an angular distance of approximately 60degrees apart.

In an embodiment, a series of first terminal conductive tracks 330 aredisposed on the first surface 316 around the slots 314. Similarly, aseries of second terminal conductive tracks 332 are disposed on thesecond surface 318 opposite conductive tracks 330 and around the slots314. A series of through-holes 334 (in this example four through-holesper slot) is disposed around each slot 314 through the first and secondconductive tracks 330 and 332.

In an embodiment, the drains of the low-side switches 324 are connectedto the corresponding first conductive tracks 330. Similarly, the sourcesof the high-side switches 322 are electrically connected to thecorresponding second conductive tracks 332. In an embodiment, as will bediscussed later, power terminals electronically connect the first andsecond conductive tracks 330 and 332 through the through-holes 334. Thisconnection provides the electrical coupling between the motor phases(PU, PV, and PW in FIG. 6) and the corresponding high-side and low-sideswitches 322 and 324. Additionally and/or alternatively, in anembodiment, through-holes 334 are vias that provide the electricalconnection between the first and second conductive tracks 330 and 332.

In an embodiment, the drains of the high-side switches 322 and thesources of the low-side switches 324 are electrically coupled to thepower supply (e.g., the B+ and B− nodes of the battery pack).

In an embodiment, control portion 340 includes controller 230, which maybe a micro-controller or other programmable control unit, mounted on thefirst surface 316 of the PCB 310. Gate driver chip 232 is similarlymounted on the first surface 316 of the PCB 310. The gate driver 232 iselectrically coupled to the gates of the high-side and low-side switches322 and 324. Other control circuitry such as power supply regulator 234components, control circuitry for on/off or speed control, etc. are alsomounted with the control portion 340 on either surface of the PCB 310.

In an embodiment, a series of pins 235 are mounted on the second surface318 of the PCB 310. Two of the pins 235 may be used, in an embodiment,to deliver power from a power supply such as a battery pack. These pinsmay be coupled to the drain of the high-side switches 322 and thesources of the low-side switches 324 via conductive tracks in the PCB310. Other pins 235 may also be used to communicate with the powersupply and/or other power tool components. These pins may be used, forexample, to communicate battery sensed voltage, battery temperature,tool temperature, and LED control to and from the controller 230.

In an embodiment, the positional sensors 238 (i.e., Hall sensors) areprovided around the through-hole 312. The positional sensors 238 may beprovided within the control portion 340 at close radial proximity to thethrough-hole 312 (e.g., approximately 1-3 mm) and at an angular distanceof approximately 60 degrees from one another. These positional sensors238 are electrically coupled to the controller 230 to provide positionalinformation of the rotor to the controller 230.

In an embodiment, in many power tool applications within the voltagerange of 10-60V as described above, high-side and low-side switches 322may be relatively small FETs with very low Rds-ON (drain-to-sourceresistance in saturation) and very low junction-to-tab thermalresistance. Thus the FETs generate low heat and transfer the heatquickly to the PCB 310. Accordingly, a relatively small heat sink issufficient to efficiently transfer heat away from the FETs withoutsacrificing the module size and performance.

In an embodiment, as shown in the perspective view of FIG. 9, a primaryheat sink 350 is surface-mounted on the first surface 316 of the PCB 310substantially covering the high-side switches 324. Primary heat sink 350may include a generally U-shaped planar main body (in this exampleincluding three rectangular sub-portions arranged at approximately 120degree angles) having two outer legs 352 bend downwardly from the endsof the main body and two inner legs 354 stamped through the main body.The legs 352 and 354 are mounted on the top surface 316 of the PCB 310adjacent the high-side switches 324, holding the primary heat sink 350main body directly above the high-side switches 324, in contact with orat a close distance thereto. This allows heat to be transferred withvery low thermal resistance network from the high-side switches 324 tothe primary heat sink 350. In an embodiment, the legs 352 and 354 of theprimary heat sink 350 may be secured to one or more conductive tracks onthe PCB 310 that are electrically coupled to the drains of the high-sideswitches 324 for improved heat transfer from the high-side switches 324.

In an embodiment, as shown in the perspective views of FIGS. 10A and10B, power terminals 360 are inserted into through-holes 332 around theslots 314 on the second surface 318 of the PCB 310. In an embodiment,each power terminal 360 includes a generally U-shaped longitudinalprofile with a planar upper portion 362 and two side portions 366extending approximately perpendicularly from the upper portion 362. Theupper portions 362 include radial peripheral slots 364 that align withslots 314 of the PCB 310. Slots 364 of the power terminals 360 aredesigned and arranged to form-fittingly receive motor terminals 104therein. Thus, in an embodiment, power terminals 360 are arranged at anangular distance of approximately 60 degrees apart.

In an embodiment, each side portion 366 of the power terminals 360includes two legs 368 that is received into the through-holes 334 andcrimped on the first surface 316 of the PCB 310. These legs 368 makeelectrical contact with first and second conductive tracks 330 and 332,transferring heat away from the low-side switches 324.

In an embodiment, as shown in FIG. 11, an electrically-isolatingthermally-conductive gap pad 370 is provided over primary heat sink 350.In an embodiment, gap pad 370 is provided with the same generalupper-surface shape as the upper surface of the primary heat sink 350.As explained below, this gap pad 370 transfers heat away from theprimary heat sink 350 to a larger secondary heat sink.

Referring to perspective top views of FIGS. 12A and 12B, and theperspective bottom view of FIG. 12C, a module housing 380 of combinedcontrol and power module 300 is described herein, according to anembodiment. In an embodiment, module housing 380 includes a secondaryheat sink 382 and a casing 384 molded around the secondary heat sink 382as shown in these figures. In an embodiment, secondary heat sink 382includes a ring-shaped or C-shaped profile with a greater surface areathan primary heat sink 350. In an embodiment, secondary heat sink 382has a surface area that is 2 to 4 times greater than primary heat sink350. The size, shape, surface area, and thickness of heat sink 350 maybe adapted based on the power tool output requirements and thecharacteristics of the power switches. For example, larger FETs forhigher-power applications may require a larger secondary heat sink 382.

In an embodiment, casing 384 is molded (i.e., via insert-molding,injection-molding, or any other known molding method) around thesecondary heat sink 382 to form a housing for the PCB 310.Alternatively, casing 383 may be provided as a separate part and laterassembled with the secondary heat sink 382. In an embodiment, casing 384includes a ring-shaped outer wall 386 and a middle portion 388 connectedto the outer wall 386 via one or more radial bridges 390. Secondary heatsink 382 includes one or more channels 392 within which bridges 390 areformed during the molding process. In this arrangement, the two surfacesof the secondary heat sink 382 are substantially uncovered by the casing384.

In an embodiment, middle portion 388 of the casing 384 includes aring-shaped longitudinal inner wall 394 defining a through-hole 396therein in the center of the casing 384. Extending radially from theinner wall 394 is a disc-shaped planar portion 398 from which the radialbridges 390 extend out to the outer wall 386. In an embodiment, planarportion 398 is formed secondary heat sink 382 is formed inside thecircular body of the secondary heat sink 382. In an embodiment, planarportion 398 includes a series of longitudinal openings 400 (in this casethree openings), which, as explained below, receives the positionalsensors 238 therein.

In an embodiment, the outer wall 386 includes a series of peripheralchannels 401 formed via a series of depressions 403 inwardly-projectingfrom the outer wall 386 towards the inner wall 394. Peripheral channels401 correspond to and align with slots 314 of the PCB 310. Whenassembled, as explained below, depressions 403 and the outer wall 384form a continuous wall within the slots 314 while the peripheralchannels 401 provide a path for motor terminals 104 to be receivedwithin slots 364 of power terminals 360.

In an embodiment, as shown in FIG. 12C, one or more locating pins 402are secured to the casing 382. In an embodiment, locating pins 402 matewith corresponding holes in the motor housing 29 for proper alignment ofthe combined control and power module 300 with the motor 28.

In an embodiment, as shown in FIGS. 13A and 13B, a gasket 404 isprovided for sealing the outer perimeter of the openings 400 during thepotting process, as described below in detail. In an embodiment, gasket404 includes a series of openings 406 corresponding to openings 400 ofthe casing 382.

FIG. 14 provides an exploded view of the combined control and powermodule 300, showing PCB 310 prior to assembly inside module housing 380.In an embodiment, the first surface 316 of the PCB 310 faces the modulehousing 380 such that the primary heat sink 350 (andthermally-conductive gap pad 370) rest on top of the secondary heat sink382 when fully assembled.

FIGS. 15A and 15B depict top and bottom assembled views of the combinedcontrol and power module 300, showing PCB 310 after assembly insidemodule housing 380, according to an embodiment. In an embodiment, whenfully inserted, depressions 403 of the outer wall 386 are receivedwithin slots 314 of the PCB 310 such that motor terminals 360 arepositioned above the depressions 403 in contact with or at a closedistance thereto, with slots 364 of the motor terminals 360 aligningwith peripheral channels 401 of the outer wall 386. Also, when fullyinserted, the first surface 316 of PCB 310 rests partially on the gasket404, and positional sensors 238 of PCB 310 are received within openings400 of the planar portion 398 of the module housing 380.

In an embodiment, in order to seal the electronic components describedherein from contamination, the module housing 380 is potted via apotting compound 410, as shown in FIG. 16. The potting compound 410flows through gaps between the PCB 310 and the outer wall 386 to fillthe underside of the PCB 310. Gasket 404 prevents flow of the pottingcompound 410 around the positional sensors 238. In an embodiment, thepotting compound covers substantially both surfaces of the PCB 310, butleaves upper portions 362 of motor terminals 360 substantially exposed.In an embodiment, pins 235 also project out of the potting compound 410.In an embodiment, as shown in FIG. 17, adhesive 412 is applied toopenings 400 to cover the positional sensors 238.

The embodiments described above provides many advantages overconventional designs, where the positional sensors, power components,and control components are provided in different modules. Since thepositional sensors, control components, and power components are allprovided on the same PCB, and routed together via metal routings on orthrough the PCB layers, there is no longer a need to wire thesecomponents together within the power tool. This substantially easer theassembly process and reduces costs. Also, since the module heat sink(i.e., secondary heat sink 382) is positioned adjacent and facing themotor 28, substantial air flow generated by the motor fan 60 passes overthe module heat sink, transferring significant amount of heat away fromthe power components.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

The invention claimed is:
 1. An electronic module for a power toolhaving an electric motor, comprising: a printed circuit board (PCB)having a first surface and a second surface; a first plurality of powerswitches mounted on the first surface of the PCB; a second plurality ofpower switches mounted on the PCB and electrically coupled to the firstplurality of power switches forming an inverter bridge circuit fordriving the electric motor; a first heat sink surface-mounted on thefirst surface of the PCB and having a planar main body disposed over thefirst plurality of power switches; a module housing arranged to receivethe PCB therein, the module housing including a planar portion facingthe first surface of the PCB and an outer wall extending from the planarportion around the PCB; and a second heat sink secured to the planarportion of the module housing in thermal communication with the firstheat sink to transfer heat from the first plurality of power switches,wherein a first surface of the second heat sink is positioned inphysical contact with the planar main body of the first heat sinkdirectly or via a thermally-conductive gap pad therebetween, and asecond surface of the second heat sink is at least partially exposed onan outer portion of the module housing facing the electric motor.
 2. Theelectronic module of claim 1, wherein each of the second plurality ofpower switches is mounted on the second surface the PCB substantiallyopposite a respective one of the first plurality of power switches. 3.The electronic module of claim 2, further comprising a first pluralityof conductive tracks disposed on the first surface of the PCB andelectrically coupled to respective drains of the first plurality ofpower switches, and a second plurality of conductive tracks disposed onthe second surface of the PCB and electrically coupled to respectivesources of the second plurality of power switches.
 4. The electronicmodule of claim 3, wherein the PCB comprises a plurality ofthrough-holes between the corresponding ones of the first plurality ofconductive tracks and the second plurality of conductive tracks, and aplurality of power terminals each having legs received within theplurality of through-holes to electrically connect the correspondingones of the first plurality of conductive tracks and the secondplurality of conductive tracks.
 5. The electronic module of claim 4,wherein each of the plurality of power terminals includes a radialperipheral slot arranged to receive and make electrical contact with acorresponding one of a plurality of motor terminal therein.
 6. Theelectronic module of claim 5, further comprising a plurality ofperipheral slots disposed around the PCB arranged for pass-through ofthe plurality of motor terminals.
 7. The electronic module of claim 1,further comprising a plurality of positional sensors disposed angularlyaround a center of the first surface of the PCB.
 8. The electronicmodule of claim 7, wherein the module housing comprises a plurality ofopenings disposed in the planar portion angularly around a center of themodule housing and corresponding to the plurality of positional sensors.9. The electronic module of claim 1, wherein the module housingcomprises a casing molded around the second heat sink.
 10. Theelectronic module of claim 1, wherein the second heat sink includes aring-shaped or a C-shaped profile.
 11. The electronic module of claim10, wherein the planar portion of the module housing comprises anon-conductive middle portion forming a central through-holetherethrough and a plurality of radial bridges extending radially fromthe non-conductive middle portion to the outer wall.
 12. The electronicmodule of claim 1, wherein the second heat sink includes a surface areathat is two to four times larger than a surface area of the first heatsink.
 13. The electronic module of claim 1, wherein the module housingand the PCB each comprises a through-hole arranged to receive a shaft ofthe electric motor therein.
 14. The electronic module of claim 1,wherein the first plurality of power switches is disposed on one side ofthe first surface of the PCB.
 15. A power tool comprising: a housingarranged to house the electric motor; and the electronic module of claim1 disposed within the housing adjacent the motor.
 16. An electronicmodule for a power tool having an electric motor, comprising: a printedcircuit board (PCB) having a first surface and a second surface; a firstplurality of power switches mounted on the first surface of the PCB; asecond plurality of power switches mounted on the PCB and electricallycoupled to the first plurality of power switches forming an inverterbridge circuit for driving the electric motor; a first heat sinksurface-mounted on the first surface of the PCB and having a planar mainbody disposed over the first plurality of power switches; a modulehousing arranged to receive the PCB therein, the module housingincluding a planar portion facing the first surface of the PCB and anouter wall extending from the planar portion around the PCB; and asecond heat sink secured to the planar portion of the module housing inthermal communication with the first heat sink to transfer heat from thefirst plurality of power switches, wherein the second heat sink includesa ring-shaped or a C-shaped profile, wherein the planar portion of themodule housing comprises a non-conductive middle portion forming acentral through-hole therethrough and a plurality of radial bridgesextending radially from the non-conductive middle portion to the outerwall, and wherein the second heat sink comprises a plurality of channelsarranged to receive the plurality of radial bridges.